KUALA LUMPUR (Reuters) - U.S Secretary of state John Kerry said on Thursday he had "zero communication" with anyone in the U.S. administration on a Pacific trade pact in connection with Malaysia's upgraded designation on human trafficking.

The State Department late last month took Malaysia off its list of worst offenders in human trafficking, removing a potential barrier to a signature Asia-Pacific trade pact, despite opposition from human rights groups and nearly 180 U.S. lawmakers.

"Let me just be crystal clear, because I am the person who approved this, I personally signed off on it, I had zero conversation with anyone in the administration about the Trans Pacific partnership relative to this decision," Kerry said in the Malaysian capital, where he has been attending a regional conference.

On Tuesday, senior U.S. lawmakers expressed concern about whether the State Department's annual global report on human trafficking may have been watered down due to political considerations and vowed to demand a full accounting at a Senate hearing this week.

Human rights groups also called for an investigation into why strategically important countries such as Malaysia were upgraded in the report, after a Reuters article chronicled how senior U.S. diplomats repeatedly overruled State Department human rights experts.

"Obviously the Congress has a right … they have every right in the world to take a look to see whether or not it's being implemented in the way Congress intended. I am absolutely confident in the work that our TIP (Trafficking in Persons) team does, which literally takes an entire year to do," Kerry said.